On Sundays, and some Saturdays, a Dominican family does a BBQ type setup right in the middle of the beach...they have whole fried fish, fried chicken, sometimes pork chops and other meat dishes...along with rice, moro, tostones, yucca, guineos, salad, etc. A plate is about 250 pesos, depending what you pile on it...It's not for everybody, but I HIGHLY recommend it if you want to try some authentic Dominican cooking, right on the sand.
I recently ate at the Black Box and I can say the burger was very good and only about 100 pesos, 150 with fries I think. It tasted like a pre-made burger from the US...not angus, but imported...not sure if that's the case, but I'd recommend it if you want a decent burger on the beach. Ive heard the rest of the menu is good as well and they have an all you can eat BBQ on Thursdays at 5pm.